already answered here but ill copy the guide:
https://stackoverflow.com/questions/2282953/tfs-2010-sharepoint-web-part-error
1.Open Team Explorer
2.Right click your [TeamProject]
3.Select Team Project Settings > Group Membership
4.Select [TeamProject]\Readers group and click properties
5.Add your user or team groups
also a more detailed guide:
http://msdn.microsoft.com/en-us/library/ms181475(v=vs.100).aspx
Team project settings and properties vary from team project to team
project. The team project properties are set from the Team menu in
Visual Studio and define settings for groups and permissions which
identify members of the team project and their access rights. For
example, one software developer may have access to change document X
in a team project but not document Y, while another software developer
involved in the same team project may have access to change both
documents X and Y. Assigning groups helps to establish the various
sub-teams within the team project and to better manage the required
tasks. Team project settings also include the virtual hierarchical
groupings for artifacts within a team project. The classification
structure may include the life cycle iterations that make up a team
project and the components or features of a team project. Work items
and other artifacts such as test cases, may also be classified against
the structures/hierarchies to make for easier tracking and reporting.
http://msdn.microsoft.com/en-us/library/ms181234(v=vs.90).aspx
not saying that you didnt back it up properly! but just incase here is a guid on msdn:
http://msdn.microsoft.com/en-us/library/bb552295.aspx
EDIT
for the error:
This site doesn't have a default Team Project. You can explicitly
select a specific Team Project. This web part is not configured
properly. Click here to configure web part in tool pane.
cause
At it's core this is a communication problem between SharePoint and
the Team Foundation Server, and there may be any number of reasons for
it, including network connectivity problems. This may also be caused
by missing or incorrect Portal Settings for the Team Project in
question, or by missing or incorrect Alternate Access Mappings in
SharePoint. Finally, it may be caused by missing permissions for the
[TEAM FOUNDATION]\SharePoint Web Application Services group to the
team project.
solution
You should first verify proper connectivity between the TFS
application tier machine(s) and those hosting SharePoint. Then, using
the Team Foundation Server Administration Console, verify that the
SharePoint Web Applications entry for the Application Tier and
SharePoint Web Application in question are established and working.
You can use the "Repair Connection" option to confirm this:
1.Open the Team Foundation Server Administration Console
2.Expand the Application Tier in question (the one hosting the Team Project Collection and Team Project with the problem)
3.Highlight the SharePoint Web Applications node.
4.In the SharePoint Web Applications list, highlight the appropriate connection and then click "Repair Connection"
While you are here, verify the membership in the Service Accounts for
SharePoint Web Applications as well.
If the "Repair Connection" is successful, next verify the Portal
Settings for the Team Project in question. You access this by
connecting to the Team Project using Team Explorer. Then, right-click
the Team Project name and select "Team Project Settings..." followed
by the "Portal Settings..." option. Ensure the values here are
correct.
You may also need to update your Alternate Access Mappings in
SharePoint (see the More Information section below for details on
this).
Also verify that in the “Extension for SharePoint Products” in TFS
Administration Console section, make sure that the “Integration
Target” column is pointing to the new or fully qualified domain name
that you expect in the Team Web Access URL for the TFS Sharepoint
portal.
To modify:
Click and highlight the row, select “Modify Access”.
Then update the “URL for Team Foundation Server” accordingly.
Click OK, and then test to see if the TSWA URL is now updated.
other solution if fails follow on here:
http://support.microsoft.com/kb/2451685
